Setting Addon options

Its been quite unclear on how to set addon configuration values.
I am trying to change the host of the onboarding app but am unable to.

Steps to reproduce the problem:
  1. mitmproxy -T --host --set or mitmproxy --host
  2. Navigate to on your iphone/browser (with the root certificate installed)
  3. 404 is returned
Any other comments? What have you tried so far?

I am fairly certain that I am not setting the values correctly. But I cant seem to figure out how to use options, get options.

System information

mitmproxy 0.18.2

Update 1

I now understand that is rightly returning 404. As there is no dns mapping pointing to localhost.

However I cant seem to figure out where to set this DNS entry.
I tried /etc/hosts but that does not seem to work.